Stucco Exterior with Cement panel interior underneath drywall.

I cut a hole in the wall of my house so I could create a space for an in wall A/C.

I found the wall was not plaster & lathe, but drywall with a 3.5 gap filled with blown insulation, then there is a 2.5" thick layer of what appears to be concrete with random reinforcement wire running horizontally.

After that there is a 3" open gap with no insulation.

Then there appears to be some type of an exterior concrete panel attached to a 1 x 4 that creates the 3" space.

Although I haven't knocked through the exterior concrete, there appears to be a series of concrete panels of which a stucco finish has been applied to its exterior surface.

I thought I had the typical plaster lathe house with a tradiotnal exterior of wire mesh and stucco exterior surface.